Family-based studies to identify genetic variants that cause congenital heart defects

Congenital heart disease risk loci identified by genome-wide association study in European patients

Genetic factors undoubtedly affect the development of congenital heart disease (CHD) but still remain ill defined. We sought to identify genetic risk factors associated with CHD and to accomplish a functional analysis of SNP-carrying genes. We performed a genome-wide association study (GWAS) of 4034 White patients with CHD and 8486 healthy controls. One SNP on chromosome 5q22.2 reached genome-wide significance across all CHD phenotypes and was also indicative for septal defects. One region on chromosome 20p12.1 pointing to the MACROD2 locus identified 4 highly significant SNPs in patients with transposition of the great arteries (TGA). Three highly significant risk variants on chromosome 17q21.32 within the GOSR2 locus were detected in patients with anomalies of thoracic arteries and veins (ATAV). Genetic variants associated with ATAV are suggested to influence the expression of WNT3, and the variant rs870142 related to septal defects is proposed to influence the expression of MSX1. We analyzed the expression of all 4 genes during cardiac differentiation of human and murine induced pluripotent stem cells in vitro and by single-cell RNA-Seq analyses of developing murine and human hearts. Our data show that MACROD2, GOSR2, WNT3, and MSX1 play an essential functional role in heart development at the embryonic and newborn stages.

Congenital heart diseases: genetics, non-inherited risk factors, and signaling pathways

Background

Congenital heart diseases (CHDs) are the most common congenital anomalies with an estimated prevalence of 8 in 1000 live births. CHDs occur as a result of abnormal embryogenesis of the heart. Congenital heart diseases are associated with significant mortality and morbidity. The damage of the heart is irreversible due to a lack of regeneration potential, and usually, the patients may require surgical intervention. Studying the developmental biology of the heart is essential not only in understanding the mechanisms and pathogenesis of congenital heart diseases but also in providing us with insight towards developing new preventive and treatment methods.

Main body

The etiology of congenital heart diseases is still elusive. Both genetic and environmental factors have been implicated to play a role in the pathogenesis of the diseases. Recently, cardiac transcription factors, cardiac-specific genes, and signaling pathways, which are responsible for early cardiac morphogenesis have been extensively studied in both human and animal experiments but leave much to be desired. The discovery of novel genetic methods such as next generation sequencing and chromosomal microarrays have led to further study the genes, non-coding RNAs and subtle chromosomal changes, elucidating their implications to the etiology of congenital heart diseases. Studies have also implicated non-hereditary risk factors such as rubella infection, teratogens, maternal age, diabetes mellitus, and abnormal hemodynamics in causing CHDs.

These etiological factors raise questions on multifactorial etiology of CHDs. It is therefore important to endeavor in research based on finding the causes of CHDs. Finding causative factors will enable us to plan intervention strategies and mitigate the consequences associated with CHDs. This review, therefore, puts forward the genetic and non-genetic causes of congenital heart diseases. Besides, it discusses crucial signaling pathways which are involved in early cardiac morphogenesis. Consequently, we aim to consolidate our knowledge on multifactorial causes of CHDs so as to pave a way for further research regarding CHDs.

Conclusion

The multifactorial etiology of congenital heart diseases gives us a challenge to explicitly establishing specific causative factors and therefore plan intervention strategies. More well-designed studies and the use of novel genetic technologies could be the way through the discovery of etiological factors implicated in the pathogenesis of congenital heart diseases.

Advances in molecular genetics for pulmonary atresia

Genetic and environmental factors may be similar in certain CHD. It has been widely accepted that it is the cumulative effect of these risk factors that results in disease. Pulmonary atresia is a rare type of complex cyanotic CHD with a poor prognosis. Understanding the molecular mechanism of pulmonary atresia is essential for future diagnosis, prevention, and therapeutic approaches. In this article, we reviewed several related copy number variants and related genetic mutations, which were identified in patients with pulmonary atresia, including pulmonary atresia with ventricular septal defect and pulmonary atresia with intact ventricular septum.

Pedigree-based Analysis of Inherited and Noninherited Risk Factors of Congenital Heart Defects

BACKGROUND

Although congenital heart defect (CHD) pedigrees are rare, they are generally taken as evidence of the existence of a genetic etiologic mechanism or environmental factors common to family members, or a combination of both. Therefore, the analysis of CHD pedigrees is important for bridging the gap in our knowledge of its etiology.

AIMS

To assess the prevalence of CHD and evaluate the nongenetic factors in the CHD patients and healthy controls in the pedigrees.

STUDY DESIGN

Observational retrospective study.

SUBJECTS

Twenty-three CHD pedigrees were involved in the prevalence statistics; thirty-nine CHD cases and fifty-two healthy controls in the CHD pedigrees were included in the family-based noninherited factors analysis.

OUTCOME MEASURES

The three-degree relatives and overall CHD prevalence were calculated. Thirty-four noninherited risk factors were compared between the CHD and control groups, first by univariate analysis and later by multivariable logistic stepwise regression analysis.

RESULTS

The CHD prevalence of the probands' relatives in all pedigrees was 8.0%, and it was 10.9%, 2.9% and 11.9% in first-, second- and third-degree relatives, respectively. The three risk factors, including maternal febrile illnesses (OR=14.2, 95%CI: [1.5 - 133.7]), influenza (OR=6.9 [2.0 - 23.6]) and air pollution (OR=13.5 [2.6 - 70.5]), were strongly associated with a higher risk of CHD in our sample.

CONCLUSIONS

For the cluster and high prevalence of CHD in the collected pedigrees, our study confirms that genetic factors play a major role in the pathogenesis of CHD, while environmental factors, such as maternal febrile illnesses, influenza and air pollution, may also increase the burden of risk for CHD pathogenesis.